Volunteered Geographic Information (VGI) is becoming increasingly important in a number of scientific and development domains, and OpenStreetMap (OSM) represents the largest effort to date to harness the power of the internet for crowd-sourced spatial data generation. OpenStreetMap was launched in 2004, initially focusing on mapping the United Kingdom. At that time, Ordnance Surveys and National Mapping Agencies developed roads datasets but did not freely distribute them, and openly available roads data such as VMAP0 were of poor quality. In April 2006, the OpenStreetMap Foundation was established to encourage the growth, development and distribution of free geospatial data and provide geospatial data for anybody to use and share. OSM now has more than 2.3 million registered users, and has mapped more than 34 million km of roads in all countries.

From the early days there has been a need to ensure the quality and accuracy of member contributions. In his presentation, Mikel Maron will describe the evolution of approaches to provide guidance to members and of applying QA/QC to the data set, including recent work by MapBox. In a second portion, Paola Kim-Blanco will summarize the literature on independent validation of OSM and describe CIESIN’s efforts to validate the data in low income countries.